Funds are requested for purchase of a STEM Analytical Electron Microscope with-ray analyzer and ancillary equipment for proper preparation and maintenance of frozen thin sections for elemental analysis. Such instrumentation would: 1. broaden the research capabilities within the institution. Present electron microscopic instrumentation cannot carry out X-ray elemental analysis of hydrated frozen thin sections necessary to answer important localization and quantitation questions of current NIH grantees. 2. upgrade existing equipment. All institutional electron microscopes are 10-16 years old and rapidly deteriorating. The STEM has separate dedicated TEM and SEM circuits which would allow the removal of older, marginally operational electron microscopes. 3. allow future accessory additions which would permit further integration of more analytical information from the same specimens. The following projects will be carried out by the major NIH users on the STEM analytical electron microscope: (1) Correlation of the amount and position of glycosaminoglycans to the morphological events during normal and experimental heart development; (2) Quantitation of the intracellular renal concentrations of key inorganic ions (Ca++, Mg++ and Na++ following administration of specific kidney toxins; (3) Determination of the relationship of intracellular Ca++ levels and calmodulin with growth rate and differentiation of chemically transformed cells; (4) Development of a powerful new tool for identification and quantitation of peptide synthesis in the CNS and pituitary gland by combining electron microscopic immunocytochemistry and in situ molecular hybridization in the same thin section; (5) Determination of the Ca++ and Co++ relationship in vascular smooth muscle of normo- and hypertensive animals. Another study will localize gold labeled antibodies to different components within hypertensive lesions; (6) Quantitation of K+/H+ antiporter in mitochondrial membranes; and (7) Quantitation and localization of Ni++ binding sites with H3- Arginine vasopressin in synapsis of the hippocampus.